Inspired equal measure by “City of God” and pop musical melodramas like “Dreamgirls” and “8 Mile,” the Brazilian film “Antônia” works low-budget wonders with its gritty locations, nonprofessional cast, and handheld documentary-style camera. Director Tata Amaral tells the story of young female empowerment sparked by the São Paulo hip-hop scene — using some of its stars as actors — while also detailing, in heartrending fashion, the forbidding obstacles that trip up or stomp down teenage aspirations.

“Antônia” is the name of the hiphop group four girlfriends have created, a way to step up to the footlights instead of serving as back-up singers to other rappers and DJs. Much like real-life girl groups such as TLC or Destiny’s Child, each member has her own distinct personality, rapping style, and skin tone, and each has her own set of problems.

When they begin, Preta (Negra Li), Lena (Cindy Mendes), Barbarah (Leilah Moreno), and Mayah (Jacqueline Simão) are sisterly solidarity personified. Their impromptu debut performance is a huge hit with a rowdy outdoor party audience. But things begin to go wrong immediately: The boyfriend Preta just dumped tries to hook up with Mayah, which ruptures their friendship; Barbarah’s gay brother, with whom she lives in a dismal cement block tenement in the hills above the city, is severely beaten; Lena becomes pregnant, and her boyfriend insists she quit the group if she intends to have the baby and live under his roof. There’s also a shifty-eyed manager (played with winningly amateurish verve by Brazilian rapper Thaide) who has intentions for Preta that go beyond promoting her career.

The plot turns around a game of attrition that nips everyone’s ambitions in the bud, perhaps to emphasize just how hard life is on the outskirts, and how far each girl has to reach beyond her circumstances to find her dreams. This sounds an awful lot like a lyric we’ve heard Beyoncé sing, and is the unerring template for every single “star is born” dramatic arc since the invention of the phonograph, at least. It makes “Antônia” a lot more predictable than it needs to be. Even given the film’s compassionate, socially aware agenda, this tends to compact its scope into a shoe box.

São Paulo boasts one of the hottest music scenes on the planet right now, and it would have been fun to explore its vibrant energies in greater depth, rather than merely use it as a backdrop. The performance sequences, featuring a dwindling lineup of the girls’ quartet, are genuinely moving, and also culturally revealing. On its brief tangent toward stardom, the group leaves the predominantly black crowds that nurtured it for gigs at upper-class house parties where paler Paulistas employ the girls as background musicians. In a key moment, the singers steal everyone’s ears with a spare, soulful reading of a Roberta Flack song, and leave the house in tears.

But unlike glossier filmmakers, Ms. Amaral doesn’t seem interested in staging a series of show-stopping moments and marshaling backbeats. It’s not that kind of movie. What carries the viewer instead is the unaffected performances of the young leads, and the director’s unflagging desire to reflect harsh daily realities — not as a tourist, but as someone who has ownership of the same experiences.